A standard motor-vehicle door latch specifically intended for use on a trunk like or rear hatch has a standard latch housing, a latch fork pivotal on the housing and latchingly engageable around a latch element, a latch pawl mounted on the housing for retaining the fork around the element or releasing it to free the element, and an operating lever which actuates the latch pawl. This pawl can be moved into the fork-freeing position by a manual actuator and/or by an electric actuator. The housing is typically mounted on the edge of a side door, but when used for the trunk or hatch is mounted on the edge of the opening in which the trunk or hatch fits.
A common problem with such a latch, in particular when used on a trunk lid or the like, is that even when the pawl has been actuated to free the bolt, the lid does not open, for instance because it is frozen shut. This is a fairly hazardous situation since it is then possible for the trunk lid or hatch to open at a later time, for instance when the vehicle is under way.
A solution to this problem is posed by German patent 3,406,116 filed 21 Feb. 1984 by Horst Brackmann. Here a force-storing element holds the operating lever in the release or actuated position until the fork moves into the open position. Thus if the lid stays closed, all the parts except the fork remain in the open position. The significance of this is that the latch is typically provided with a switch connected to a dashboard light that indicates the on/off condition of the trunk lid. In this arrangement the switch is actuated by the fork-operating mechanism, not by the fork, so that in this potentially dangerous situation the driver will be able to know that while the trunk or other door appears latched, in reality it is not.
In this earlier arrangement a separate rotary cam is provided for electric actuation of the latch. This cam is an essential part of the position-holding structure and without it the position-holding system cannot work. Indeed, the position-holding arrangement cannot be applied to a purely manual system.